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RAID Storage Systems -SSD vs. HDD Comparison

October 5, 2020

RAID (Redundant Array of Independent Disks) is a method of storing the same data in different locations on multiple hard disk drives (HDD) or solid-state drives (SSD) to protect data in the event of a drive failure. This method increases the speed of storing and accessing data while preventing data loss and unplanned downtimes – as data is shared over multiple disks, this increases the mean time between failures (MTBF). Storing data redundantly also increases fault tolerance. RAID data recovery utilizes the practices of disk mirroring or disk striping. Mirroring will copy identical data onto more than one drive, dependant on the RAID level chosen.

RAID works by allowing input/ output (I/O) operations to overlap in a balanced fashion, therefore improving subsequent application performance. There are different RAID levels that can be utilized (RAID level: 0, 1, 2, 3, 4, 5, 6, 10 + combinations), but not all RAID levels intend to provide redundancy.

No matter what RAID level is adopted, the RAID array will appear to the underlying operating system (OS) as a single logical drive. RAID, by tradition, was primarily designed for use in servers, but its implementation is seen in storage-intensive computers and applications that need a high level of data security and high transfer speeds.

How using SSD RAID arrays can lead to further performance gains over HDD

Let me be quite frank – SSDs are considerably more appealing as a storage component due to their high performance and minimal power consumption when compared with HDDs. SSDs tend to be far more reliable than HDDs because they do not have any moving parts that can malfunction over time with continual usage. That is not to say that SSDs are not prone to failure – they do, and can, fail for various reasons.


It is for these key reasons that SSD RAID arrays, and server data recovery, can be highly advantageous when used with business applications where data security and data protection is more than merely a requirement, but a vital component that needs to be satisfied by Information Technology providers. Add to this the fact that SSD RAID arrays can provide further performance gains than what HDD RAID arrays can deliver, it is clear that two facts become apparent:

·       HDDs are more susceptible to failure than SSDs,

·       HDDs offer lower performance than SSDs.

This distinction is crucial with our comparison objectives because a RAID array can either help you achieve improved performance or superior protection against disk failure, or both.

It is important to note that organizations that are utilizing SSDs are likely to have infrastructure workloads with specific and demanding storage requirements regarding performance. Single SSDs might struggle to provide the necessary performance service level agreements, and it’s when dealing with these circumstances that an SSD RAID array may offer the essential performance boost required. RAID arrays are likely to be the sensible storage solution to remediate performance challenges in organizations with SSD infrastructure already present and operational.

How RAID storage has changed with the migration from HDD to SSD


RAID’s positioning in the infrastructure enterprise storage world has evolved over time due to the following grounds:

·       SSDs are far more reliable devices compared with legacy HDDs. The provides the confidence that a drive failure occurrence in a RAID array much less likely to occur,

·       Firmware defined storage options that operate differently from RAID, and thus do not require the procurement of expensive RAID controllers with associated backup power requirements, but still provide protection against data loss in the event of hardware failure,

·       Server-based computing is evolving to present quicker and more straightforward options for IT consumers; potential complications with storage infrastructure systems – such as the introduction of further RAID controllers – not only increase capital expenditure but also introduces another possible failure point for CIOs to be concerned about.

These points are not meant to portray RAID as a stagnant technology that is merely watching the world pass it by – far from it. There is the concept of Differential RAID (or Diff-RAID), a new RAID variant that distributes uniformity unevenly across SSDs to create age disparities within RAID arrays. This strategy has been devised with SSDs in RAID formation to track each drive’s age within a RAID set. The controller knows how old each drive within the RAID array is, and it smartly distributes more activity to the newer drives, and less activity towards the older drives. The objective is to ensure that all drives will not experience simultaneous unrecoverable data errors. Diff-RAID provides much greater reliability for SSDs than RAID-4 and RAID-5 for the same space overhead and offers a trade-off curve between throughput and reliability.

The key technical considerations to be aware of when boosting SSD Performance with RAID

As previously mentioned, there are considerable technical differences between HDDs and SSDs, and these differences will drive the decision as to what RAID array implementation will be required to cater to both of them. Simply put, some RAID implementations are great for HDDs are not for SSDs, and vice-versa. So, the primary question that requires an answer is: which RAID level should be utilized when using an SSD RAID array?

SSD Raid 1 (Mirror):

RAID 1 can provide complete redundancy, but only simple performance gains, and therefore should be considered if performance requirements are not a vital requirement for application delivery.

SSD RAID 5 or 6:

A popular alternative that provides redundancy is RAID 5 (uses data striping with parity bits and requires a minimum of three disks) and RAID 6 (uses striping and double parity with a minimum of four disks).


A superior alternative to RAID 5 or 6 would be the adoption of SSD RAID configuration level 10. RAID 10 uses RAID stripe and mirroring to provide fault tolerance with a minimum of four SSDs. An additional advantage of RAID 10 is that it can offer a high level of performance, but with a decrease in storage efficiency. The key benefit is that any two disks can fail without losing data, and both of these RAID configurations provide increased performance. The challenges with RAID 5 and 6 are that both implementations require a large number of disk write operations to cater to the parity bit information requirement.

(Note: for data protection purposes, RAID 0 was disregarded as it uses a RAID stripe pattern written to two disks to increase performance but offers no data redundancy).


More extensive consumer storage requirements drive the necessity for IT providers and suppliers to deliver reliable, effective, and performance-oriented storage infrastructure solutions that are cost-effective and profitable. SSD RAID provides the essential tools, processes, and storage delivery mechanisms that can deliver these consumer requirements – more so than what HDD RAID can. SSDs are an order or two magnitude faster than traditional media, and their capacities more than rival what HDDs have controlled and provided all along.

SSDs do exhibit wear and tear over time; however, their lifespan is significantly longer than legacy disk drives, making their in-service dates much more predictable and maintenance activities far more efficient and reliable.